Hall sensor with buried hall plate

ABSTRACT

A CMOS integrated circuit includes a Hall sensor having a Hall plate formed in a first isolation layer which is formed concurrently with a second isolation layer under a MOS transistor. A first shallow well with a conductivity type opposite from the first isolation layer is formed over, and extending to, the Hall plate. The first shallow well is formed concurrently with a second shallow well under the MOS transistor. The Hall sensor may be a horizontal Hall sensor for sensing magnetic fields oriented perpendicular to the top surface of the substrate of the integrated circuit, or may be a vertical Hall sensor for sensing magnetic fields oriented parallel to the top surface of the substrate of the integrated circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of Ser. No. 15/639,327 filed Jun. 30,2017, which is a continuation of patent application Ser. No. 14/932,949,filed on Nov. 4, 2015, that is now U.S. Pat. No. 9,728,581 (grant dateof Aug. 8, 2017), the contents of all are incorporated by reference intheir entirety.

FIELD OF THE DISCLOSURE

This disclosure relates to the field of integrated circuits. Moreparticularly, this disclosure relates to Hall-effect magnetic sensor(Hall sensors) in integrated circuits.

BACKGROUND OF THE DISCLOSURE

It is desirable to integrate a Hall sensor into an integrated circuit toreduce system cost and complexity. As complementary metal oxidesemiconductor (CMOS) integrated circuits are increasingly used in analogcircuit systems, due to the low fabrication cost of the CMOS devicescompared to analog integrated circuits, it becomes desirable tointegrate Hall sensors into CMOS integrated circuits. A conventionalshallow well-based Hall sensor in a scaled CMOS technology has poormagnetic sensitivity due to low resistivity of the well.

SUMMARY OF THE DISCLOSURE

The following presents a simplified summary in order to provide a basicunderstanding of one or more aspects of the disclosure. This summary isnot an extensive overview of the disclosure, and is neither intended toidentify key or critical elements of the disclosure, nor to delineatethe scope thereof. Rather, the primary purpose of the summary is topresent some concepts of the disclosure in a simplified form as aprelude to a more detailed description that is presented later.

A CMOS integrated circuit includes a Hall sensor having a Hall plateformed in an isolation layer which is formed concurrently with anisolation layer under a metal oxide semiconductor (MOS) transistor. Ashallow well with a conductivity type opposite from the isolation layeris formed over, and extending to, the Hall plate. The shallow well isformed concurrently with a shallow well under the MOS transistor.

DESCRIPTION OF THE VIEWS OF THE DRAWING

FIG. 1 is a cross section of an example integrated circuit containing aHall sensor.

FIG. 2A through FIG. 2E are cross sections of the integrated circuit ofFIG. 1, depicted in successive steps of an example formation process.

FIG. 3 is a cross section of another example integrated circuitcontaining a Hall sensor.

FIG. 4 is a cross section of another integrated circuit containing aHall sensor, depicted during formation of isolation layers.

FIG. 5A through FIG. 5C are cross sections of another integrated circuitcontaining a Hall sensor, depicted steps of formation of isolationlayers.

FIG. 6 is a cross section of another example integrated circuitcontaining a Hall sensor.

FIG. 7 is a cross section of another example integrated circuitcontaining a Hall sensor.

FIG. 8 is a cross section of another example integrated circuitcontaining a Hall sensor.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present disclosure is described with reference to the attachedfigures. The figures are not drawn to scale and they are provided merelyto illustrate the disclosure. Several aspects of the disclosure aredescribed below with reference to example applications for illustration.It should be understood that numerous specific details, relationships,and methods are set forth to provide an understanding of the disclosure.One skilled in the relevant art, however, will readily recognize thatthe disclosure can be practiced without one or more of the specificdetails or with other methods. In other instances, well-known structuresor operations are not shown in detail to avoid obscuring the disclosure.The present disclosure is not limited by the illustrated ordering ofacts or events, as some acts may occur in different orders and/orconcurrently with other acts or events. Furthermore, not all illustratedacts or events are required to implement a methodology in accordancewith the present disclosure.

FIG. 1 is a cross section of an example integrated circuit containing aHall sensor. The integrated circuit 100 has a substrate 102 which maybe, for example, from a silicon wafer. The substrate 102 includes ap-type semiconductor material 104 which may be a top portion of asilicon wafer, or may be an epitaxial layer formed on a silicon wafer.The integrated circuit 100 includes a Hall sensor 106, an n-channelmetal oxide semiconductor (NMOS) transistor 108 and a p-channel metaloxide semiconductor (PMOS) transistor 110. In the instant example, theHall sensor 106 is a horizontal Hall sensor for sensing magnetic fieldsoriented perpendicular to a top surface 112 of the substrate 102. Avertical Hall sensor for sensing magnetic fields oriented parallel tothe top surface 112 is within the scope of the instant example. Theintegrated circuit 100 may include field oxide 114 disposed at the topsurface 112 of the substrate 102 to laterally isolate components andelements. The field oxide 114 may have a shallow trench isolation (STI)structure as depicted in FIG. 1. Alternatively, the field oxide 114 mayhave a localized oxidation of silicon (LOCOS) structure. Field oxidewith another structure is within the scope of the instant example.

The Hall sensor 106 includes a Hall plate 118 disposed in a first n-typeisolation layer 120 in the substrate 102. An average net dopant densityof the Hall plate 118, that is an average of a difference between n-typedopants and p-type dopants in the Hall plate 118, may be, for example,5×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³. A thickness of the Hall plate 118 may be 0.5microns to 1 micron. The average net dopant density and the thicknessmay provide a sheet resistance of 850 ohms per square to 2500 ohms persquare of the Hall plate 118. A lateral length 122 of the Hall plate 118may be, for example, 25 microns to 125 microns. Increasing the laterallength 122 may provide a higher Hall voltage from the Hall plate 118which advantageously improves a sensitivity of the Hall sensor 106.Decreasing the lateral length 122 reduces a size of the integratedcircuit which advantageously reduces fabrication cost. Forming the Hallplate 118 with the lateral length 122 of 25 microns to 125 microns mayprovide a desired balance between sensitivity and cost. The Hall sensor106 includes a first shallow p-type well 124 disposed in the substrate102 over, and extending to, the Hall plate 118. The first shallow p-typewell 124 may extend below the field oxide 114. Various structures may bedisposed in and/or over the first shallow p-type well 124 over the Hallplate 118. In the instant example, dummy active areas 116 with p-typeregions 126, separated by elements of the field oxide 114, may be formedin the first shallow p-type well 124 over the Hall plate 118 to reducenon-planarity of the top surface 112 by an oxide chemical mechanicalpolish (CMP) process during formation of the field oxide 114. Electricalconnections to the Hall plate 118 may be provided by first shallown-type wells 130 disposed in the substrate 102. FIG. 1 depicts twoexample connections to the Hall plate 118; additional connections may beout of the plane of FIG. 1. The first shallow n-type wells 130 may belaterally separated from the first shallow p-type well 124 by elementsof the field oxide 114. N-type contact regions 132 may be disposed inthe substrate 102 over the first shallow n-type wells 130 to reduceelectrical resistance to the Hall plate 118. Elements of the metalsilicide 128 may be disposed over the n-type contact regions 132 tofurther reduce electrical resistance to the Hall plate 118.

The NMOS transistor 108 is disposed over a second shallow p-type well134 disposed in the substrate 102. The first shallow p-type well 124 ofthe Hall sensor 106 and the second shallow p-type well 134 havesubstantially equal distributions of p-type dopants such as boron as aresult of being formed concurrently. The second shallow p-type well 134is contained in a second n-type isolation layer 136. The second n-typeisolation layer 136 may possibly be abutting and contiguous with thefirst n-type isolation layer 120 which provides the Hall plate 118 asdepicted in FIG. 1. Alternatively, the second n-type isolation layer 136may be separate from the first n-type isolation layer 120. In eithercase, the second n-type isolation layer 136 and the first n-typeisolation layer 120 have substantially equal distributions of n-typedopants such as phosphorus as a result of being formed concurrently. TheNMOS transistor 108 includes an NMOS gate structure 138 disposed overthe second shallow p-type well 134. The NMOS gate structure 138 includesa gate dielectric layer disposed on the top surface 112 of the substrate102, a gate disposed on the gate dielectric layer, and possibly gatesidewall spacers disposed on lateral surfaces of the gate. The NMOStransistor 108 includes n-channel source/drain (NSD) regions 140disposed in the substrate 102 adjacent to, and partially underlapping,the NMOS gate structure 138. The n-type contact regions 132 of the Hallsensor 106 and the NSD regions 140 may have substantially equaldistributions of n-type dopants such as phosphorus and arsenic as aresult of being formed concurrently. Elements of the metal silicide 128may be disposed on the NSD regions 140 to reduce electrical resistanceto the NMOS transistor 108.

The PMOS transistor 110 is disposed over a second shallow n-type well142 disposed in the substrate 102. The first shallow n-type wells 130 ofthe Hall sensor 106 and the second shallow n-type well 142 may havesubstantially equal distributions of n-type dopants such as phosphorusas a result of being formed concurrently. The PMOS transistor 110includes a PMOS gate structure 144 disposed over the second shallown-type well 142. The PMOS gate structure 144 includes a gate dielectriclayer disposed on the top surface 112 of the substrate 102, a gatedisposed on the gate dielectric layer, and possibly gate sidewallspacers disposed on lateral surfaces of the gate. The PMOS transistor110 includes p-channel source/drain (PSD) regions 146 disposed in thesubstrate 102 adjacent to, and partially underlapping, the PMOS gatestructure 144. The p-type regions 126 of the Hall sensor 106 and the PSDregions 146 may have substantially equal distributions of p-type dopantssuch as boron as a result of being formed concurrently. Elements of themetal silicide 128 may be disposed on the PSD regions 146 to reduceelectrical resistance to the PMOS transistor 110.

A pre-metal dielectric (PMD) layer 148 is disposed over the top surface112 of the substrate 102. The PMD layer 148 may include one or moresub-layers of dielectric material, for example a PMD liner of siliconnitride on the top surface 112, a layer of silicon dioxide-basedmaterial formed by a high density plasma or a chemical vapor deposition(CVD) process using tetraethyl orthosilicate (TEOS) and ozone, a layerof silicon dioxide-based material such as phosphorus silicate glass(PSG) or boron phosphorus silicate glass (BPSG), and a cap layer ofsilicon nitride, silicon oxynitride, silicon carbide or silicon carbidenitride. Contacts 150 are formed through the PMD layer 148 to makecontact to the metal silicide 128. The contacts 150 may have metalliners of titanium and titanium nitride, and fill metals of tungsten.Layers of metal interconnects and dielectric material, not shown in FIG.1, are disposed above the PMD layer 148 to provide electricalconnections between the components of the integrated circuit 100.

Increasing the average net dopant density of the second n-type isolationlayer 136 provides better electrical isolation of the NMOS transistor108 from the p-type semiconductor material 104, while decreasing theaverage net dopant density of the first n-type isolation layer 120provides higher sensitivity of the Hall sensor 106. Forming the firstn-type isolation layer 120 and the second n-type isolation layer 136 tohave an average net dopant density of 5×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³ and athickness of 0.5 microns to 1 micron advantageously provides a desiredlevel of isolation for the NMOS transistor 108 and a desired sensitivityof the Hall sensor 106. The first shallow p-type well 124 being disposedover, and in contact with, the Hall plate 118 enables an advantageousmode of operation. During operation of the integrated circuit 100, abias voltage may be applied to the first shallow p-type well 124 toreverse bias a pn junction between the first shallow p-type well 124 andthe Hall plate 118, which may advantageously increase the sensitivity ofthe Hall sensor 106. For example, the first shallow p-type well 124 maybe electrically coupled to the p-type semiconductor material 104 of thesubstrate 102, and a positive voltage applied to the Hall plate 118.Alternatively, the first shallow p-type well 124 may be floated,providing a simplified structure for the Hall sensor 106.

The integrated circuit 100 includes at least one of a current source 152electrically coupled to the Hall sensor 106 and a voltage sensor 154electrically coupled to the Hall sensor 106. The current source 152 iselectrically coupled to the Hall sensor 106 through the contacts 150, asdepicted in FIG. 1. The voltage sensor 154 is electrically coupled tothe Hall sensor 106 through other contacts 150, out of the plane of FIG.1 in the instant example. During operation of the integrated circuit100, the current source 152 provides a current through the Hall plate118, and the voltage sensor 154 senses a Hall voltage on the Hall plate118 which is a function of a magnetic field through the Hall plate 118and provides an electrical output which is a function of the Hallvoltage. Including least one of the current source 152 and the voltagesensor 154 in the integrated circuit 100 may advantageously reduce acost and complexity of a system including the integrated circuit 100.

FIG. 2A through FIG. 2E are cross sections of the integrated circuit ofFIG. 1, depicted in successive steps of an example formation process.Referring to FIG. 2A, the field oxide 114, including elements of thefield oxide 114 defining the dummy active areas 116, is formed at thetop surface 112 of the substrate 102. In one version of the instantexample, the field oxide 114 may be formed by an STI process, whichincludes etching isolation trenches in the substrate 102, filling thetrenches with dielectric material and removing excess dielectricmaterial using an oxide CMP process. In another version of the instantexample, the field oxide 114 may be formed by a LOCOS process, whichincludes patterning a layer of silicon nitride over the top surface 112of the substrate 102 to expose areas for the field oxide 114, formingthe field oxide 114 by a thermal oxidation process, and subsequentlyremoving the layer of silicon nitride.

An isolation mask 156 is formed over the substrate 102 so as to exposean area for the first n-type isolation layer 120 and an area for thesecond n-type isolation layer 136. The isolation mask 156 may includephotoresist formed by a photolithographic process, and may optionallyinclude an anti-reflection layer such as a bottom anti-reflection coat(BARC). In the instant example, the area for the Hall sensor 106 and thearea for the NMOS transistor 108 are adjacent, so the isolation mask 156exposes a contiguous area for the first n-type isolation layer 120providing the Hall plate 118 and the second n-type isolation layer 136under the NMOS transistor 108. The isolation mask 156 covers the areafor the PMOS transistor 110. N-type dopants such as phosphorus areimplanted into the substrate 102 where exposed by the isolation mask156; the isolation mask 156 blocks the n-type dopants from the substrate102. The n-type dopants may be implanted, for example, at 1000kilo-electron volts (keV) to 2000 keV with a dose of 5×10¹² cm⁻² to2×10¹³ cm⁻². The isolation mask 156 is subsequently removed, for exampleby an ash process followed by a wet clean process. The implanted n-typedopants are activated by an anneal process to form the first n-typeisolation layer 120 and the second n-type isolation layer 136. Theanneal process may include a furnace anneal process or a rapid thermalanneal process. The furnace anneal process may include a range of annealconditions from a temperature of 850° C. for 120 minutes to atemperature of 950° C. for 10 minutes. The rapid thermal anneal processmay include a range of anneal conditions from a temperature of 1000° C.for 60 seconds to a temperature of 1100° C. for 20 seconds, in a rapidthermal processor (RTP) tool. The anneal process may be performed afterthe n-type dopants are implanted and before any subsequent implants, ormay be performed after additional n-type dopants are implanted to formthe shallow n-type wells 130 and 142 of FIG. 1 and after p-type dopantsare implanted to form the shallow p-type wells 124 and 134 of FIG. 1.Concurrently forming the second n-type isolation layer 136 and the firstn-type isolation layer 120 may advantageously reduce fabrication costand complexity of the integrated circuit 100 compared to forming then-type isolation layers separately.

Referring to FIG. 2B, a p-type well mask 158 is formed over thesubstrate 102 so as to expose areas for the first shallow p-type well124 in the Hall sensor 106 and the second shallow p-type well 134 underthe NMOS transistor 108. The p-type well mask 158 covers the area forthe PMOS transistor 110. The p-type well mask 158 may includephotoresist formed by a photolithographic process, and may optionallyinclude an anti-reflection layer such as a BARC. P-type dopants such asboron are implanted into the substrate 102 where exposed by the p-typewell mask 158; the p-type well mask 158 blocks the p-type dopants fromthe substrate 102. The p-type dopants may be implanted, for example, at200 kilo-electron volts (keV) to 500 keV with a dose of 2×10¹³ cm⁻² to5×10¹³ cm⁻². Additional p-type dopants may be implanted at lowerenergies, for example to provide punch-through, channel stop andthreshold adjust layers for the NMOS transistor 108. The p-type wellmask 158 is subsequently removed, for example as described in referenceto the isolation mask 156 of FIG. 2A. The implanted p-type dopants areactivated by an anneal process to form the first shallow p-type well 124and the second shallow p-type well 134. The first shallow p-type well124 extends to the Hall plate 118. The anneal process may be, forexample, a furnace anneal process or a rapid thermal anneal process, asdescribed in reference to FIG. 2A. The anneal process may be the sameanneal process used to activate the implanted n-type dopants in thefirst n-type isolation layer 120 and the second n-type isolation layer136, or may be a separate anneal process. Concurrently forming the firstshallow p-type well 124 of the Hall sensor 106 and the second shallowp-type well 134 under the NMOS transistor 108 may advantageously furtherreduce fabrication cost and complexity of the integrated circuit 100compared to forming the shallow p-type wells separately.

Referring to FIG. 2C, an n-type well mask 160 is formed over thesubstrate 102 so as to expose areas for the first shallow n-type wells130 in the Hall sensor 106 and the second shallow n-type well 142 underthe PMOS transistor 110. The n-type well mask 160 covers the area forthe NMOS transistor 108. The n-type well mask 160 may be formedsimilarly to the p-type well mask 158 of FIG. 2B. N-type dopants such asphosphorus are implanted into the substrate 102 where exposed by then-type well mask 160; the n-type well mask 160 blocks the n-type dopantsfrom the substrate 102. The n-type dopants may be implanted, forexample, at 400 kilo-electron volts (keV) to 750 keV with a dose of2×10¹³ cm⁻² to 8×10¹³ cm⁻². Additional n-type dopants such as phosphorusand arsenic may be implanted at lower energies, for example to providepunch-through, channel stop and threshold adjust layers for the PMOStransistor 110. The n-type well mask 160 is subsequently removed, forexample as described in reference to the isolation mask 156 of FIG. 2A.The implanted n-type dopants are activated by an anneal process to formthe first shallow n-type wells 130 and the second shallow n-type well142. The anneal process may be, for example, a furnace anneal process ora rapid thermal anneal process, as described in reference to FIG. 2A.The anneal process may be the same anneal process used to activate theimplanted p-type dopants in the first shallow p-type well 124 and thesecond shallow p-type well 134, or may be a separate anneal process.Forming the first shallow n-type wells 130 of the Hall sensor 106concurrently with the second shallow n-type well 142 under the PMOStransistor 110 may advantageously further reduce fabrication cost andcomplexity of the integrated circuit 100 compared to forming the shallown-type wells separately.

Referring to FIG. 2D, the NMOS gate structure 138 of the NMOS transistor108 and the PMOS gate structure 144 of the PMOS transistor 110 areformed on the substrate 102. N-type drain extensions, not shown in FIG.2C, may be formed in the substrate 102 adjacent to the NMOS gatestructure 138, and p-type drain extensions, not shown in FIG. 2C, may beformed in the substrate 102 adjacent to the PMOS gate structure 144. AnNSD mask 162 is formed over the substrate 102 so as to expose areas forthe n-type contact regions 132 in the Hall sensor 106 and the NSDregions 140 of the NMOS transistor 108. The NSD mask 162 covers the areafor the PMOS transistor 110. The NSD mask 162 may include photoresistformed by a photolithographic process, and may include ananti-reflection layer such as a BARC. N-type dopants such as phosphorusand arsenic, and possibly antimony, are implanted into the substrate 102where exposed by the NSD mask 162; the NSD mask 162 blocks the n-typedopants from the substrate 102.

The n-type dopants may be implanted in more than one implant step withimplant energies ranging, for example, from 20 keV to 60 keV and with atotal dose of 1×10¹⁵ cm⁻² to 4×10¹⁵ cm⁻². The NSD mask 162 issubsequently removed, for example as described in reference to theisolation mask 156 of FIG. 2A. The implanted n-type dopants areactivated by an anneal process to form the n-type contact regions 132and the NSD regions 140. The anneal process may be, for example, a rapidthermal anneal process as described in reference to FIG. 2A, or a flashanneal process. An example flash anneal process uses radiant energy toheat the substrate 102 at the top surface 112 to a temperature of 1200°C. to 1250° C. for 1 millisecond to 5 milliseconds. Forming the n-typecontact regions 132 of the Hall sensor 106 concurrently with the NSDregions 140 of the NMOS transistor 108 may advantageously further reducefabrication cost and complexity of the integrated circuit 100 comparedto forming the n-type regions separately.

Referring to FIG. 2E, a PSD mask 164 is formed over the substrate 102 soas to expose areas for the p-type regions 126 in the Hall sensor 106 andthe PSD regions 146 of the PMOS transistor 110. The PSD mask 164 coversthe area for the NMOS transistor 108. The PSD mask 164 may be formedsimilarly to the NSD mask 162 of FIG. 2D.

P-type dopants such as boron and gallium, and possibly indium, areimplanted into the substrate 102 where exposed by the PSD mask 164; thePSD mask 164 blocks the p-type dopants from the substrate 102. Thep-type dopants may be implanted in more than one implant step withimplant energies ranging, for example, from 3 keV to 20 keV and with atotal dose of 1×10¹⁵ cm⁻² to 4×10¹⁵ cm⁻². The PSD mask 164 issubsequently removed, for example as described in reference to theisolation mask 156 of FIG. 2A. The implanted p-type dopants areactivated by an anneal process to form the p-type regions 126 and thePSD regions 146. The anneal process may be, for example, a rapid thermalanneal process or a flash anneal process, and may be performedconcurrently with the anneal process for the n-type contact regions 132and the NSD regions 140. Forming the p-type regions 126 of the Hallsensor 106 concurrently with the PSD regions 146 of the PMOS transistor110 may advantageously further reduce fabrication cost and complexity ofthe integrated circuit 100 compared to forming the p-type regionsseparately.

Formation of the integrated circuit 100 is continued with forming themetal silicide 128 of FIG. 1 on exposed semiconductor material at thetop surface 112 of the substrate 102. Subsequently, the PMD layer 148and the contacts 150 are formed to provide the structure of FIG. 1. AHall sensor analogous to that disclosed in reference to FIG. 1 and FIG.2A through FIG. 2E may be formed with a p-type Hall plate, byappropriate changes in polarities of dopants and conductivity types.

FIG. 3 is a cross section of another example integrated circuitcontaining a Hall sensor. The integrated circuit 300 has a substrate 302including a p-type semiconductor material 304. The integrated circuit300 includes a Hall sensor 306, an NMOS transistor 308 and a PMOStransistor 310. In the instant example, the Hall sensor 306 is avertical Hall sensor for sensing magnetic fields oriented parallel to atop surface 312 of the substrate 302. A horizontal Hall sensor forsensing magnetic fields oriented perpendicular to the top surface 312 iswithin the scope of the instant example. The integrated circuit 300 mayinclude field oxide 314 disposed at the top surface 312 of the substrate302 to laterally isolate components and elements.

The Hall sensor 306 includes a Hall plate 318 disposed in a first n-typeisolation layer 320 in the substrate 302. An average net dopant densityof the Hall plate 318 may be, for example, 5×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³. Athickness of the Hall plate 318 may be 0.5 microns to 1 micron. Theaverage net dopant density and the thickness may provide a sheetresistance of 850 ohms per square to 2500 ohms per square of the Hallplate 318. A lateral length 322 of the Hall plate 318 may be, forexample, 50 microns to 125 microns for a vertical Hall sensor. Formingthe Hall plate 318 with the lateral length 322 of 50 microns to 125microns may provide a desired balance between sensitivity and cost. TheHall sensor 306 includes first shallow p-type wells 324 disposed in thesubstrate 302 over, and extending to, the Hall plate 318. The firstshallow p-type wells 324 may extend below the field oxide 314 and maypossibly be contiguous at locations out of the plane of FIG. 3. Thefirst shallow p-type wells 324 may be biased or floated, as described inreference to the first shallow p-type well 124 of FIG. 1, accruing theadvantages disclosed therein. Various structures may be disposed inand/or over the first shallow p-type wells 324 over the Hall plate 318.In the instant example, p-type regions 326 may be disposed in the firstshallow p-type wells 324 and a layer of silicide block dielectric 366disposed over the p-type regions 326. Electrical connections to the Hallplate 318 may be provided by first shallow n-type wells 330 disposed inthe substrate 302. FIG. 3 depicts four example connections to the Hallplate 318; the Hall sensor 306 may include additional connections. Thefirst shallow n-type wells 330 may be laterally separated from the firstshallow p-type wells 324 by elements of the field oxide 314. N-typecontact regions 332 may be disposed in the substrate 302 over the firstshallow n-type wells 330 to reduce electrical resistance to the Hallplate 318. Elements of the metal silicide 328 may be disposed over then-type contact regions 332 to further reduce electrical resistance tothe Hall plate 318.

The NMOS transistor 308 is disposed over a second shallow p-type well334 disposed in the substrate 302. The first shallow p-type wells 324 ofthe Hall sensor 306 and the second shallow p-type well 334 havesubstantially equal distributions of p-type dopants such as boron as aresult of being formed concurrently, for example as described inreference to FIG. 2B. The second shallow p-type well 334 is contained ina second n-type isolation layer 336, which may be separate from thefirst n-type isolation layer 320 which provides the Hall plate 318 asdepicted in FIG. 3. Alternatively, the second shallow p-type well 334may be contained in a common n-type isolation layer which provides theHall plate 318, as described in reference to FIG. 1. In either case, thesecond n-type isolation layer 336 containing the second shallow p-typewell 334 and the first n-type isolation layer 320 which provides theHall plate 318 have substantially equal distributions of n-type dopantssuch as phosphorus as a result of being formed concurrently, for exampleas described in reference to FIG. 2A. The NMOS transistor 308 includesan NMOS gate structure 338 disposed over the second shallow p-type well334 and NSD regions 340 disposed in the substrate 302 adjacent to, andpartially underlapping, the NMOS gate structure 338, similar to thatdescribed in reference to FIG. 1. The n-type contact regions 332 of theHall sensor 306 and the NSD regions 340 may have substantially equaldistributions of n-type dopants such as phosphorus and arsenic as aresult of being formed concurrently, for example as described inreference to FIG. 2D. Elements of the metal silicide 328 may be disposedon the NSD regions 340 to reduce electrical resistance to the NMOStransistor 308.

The PMOS transistor 310 is disposed over a second shallow n-type well342 disposed in the substrate 302. The first shallow n-type wells 330 ofthe Hall sensor 306 and the second shallow n-type well 342 may havesubstantially equal distributions of n-type dopants such as phosphorusas a result of being formed concurrently, for example as described inreference to FIG. 2C. The PMOS transistor 310 includes a PMOS gatestructure 344 and PSD regions 346 disposed in the substrate 302 adjacentto, and partially underlapping, the PMOS gate structure 344, similar tothat described in reference to FIG. 1. The p-type regions 326 of theHall sensor 306 and the PSD regions 346 may have substantially equaldistributions of p-type dopants such as boron as a result of beingformed concurrently, for example as described in reference to FIG. 2E.Elements of the metal silicide 328 may be disposed on the PSD regions346 to reduce electrical resistance to the PMOS transistor 310.

In the instant example, the integrated circuit 300 may also include asubstrate tap 368 which provides an electrical connection to the p-typesemiconductor material 304. The substrate tap 368 includes a thirdshallow p-type well 370 disposed in the substrate 302. The first shallowp-type wells 324 of the Hall sensor 306 and the third shallow p-typewell 370 have substantially equal distributions of p-type dopants suchas boron as a result of being formed concurrently, for example asdescribed in reference to FIG. 2B. The substrate tap 368 also includes ap-type contact region 372 disposed in the third shallow p-type well 370.The p-type regions 326 of the Hall sensor 306 and the p-type contactregion 372 may have substantially equal distributions of p-type dopantssuch as boron as a result of being formed concurrently, for example asdescribed in reference to FIG. 2E. An element of the metal silicide 328may be disposed on the p-type contact region 372 to reduce electricalresistance to the p-type semiconductor material 304. A Hall sensoranalogous to that disclosed in reference to FIG. 3 may be formed with ap-type Hall plate, by appropriate changes in polarities of dopants andconductivity types.

A PMD layer 348 and contacts 350, for example as described in referenceto FIG. 1, are disposed over the top surface 312 of the substrate 302.Layers of metal interconnects and dielectric material, not shown in FIG.3, are disposed above the PMD layer 348 to provide electricalconnections between the components of the integrated circuit 300. Theintegrated circuit 300 accrues the advantages discussed in reference tothe integrated circuit 100 of FIG. 1.

The integrated circuit 300 includes at least one of a current source 352electrically coupled to the Hall sensor 306 and a voltage sensor 354electrically coupled to the Hall sensor 306. The current source 352 iselectrically coupled to the Hall sensor 306 through the contacts 350, asdepicted in FIG. 3. The voltage sensor 354 is electrically coupled tothe Hall sensor 306 through other contacts 350, as depicted in FIG. 3.During operation of the integrated circuit 300, the current source 352provides a current through the Hall plate 318, and the voltage sensor354 senses a Hall voltage on the Hall plate 318 which is a function of amagnetic field through the Hall plate 318 and provides an electricaloutput which is a function of the Hall voltage.

FIG. 4 is a cross section of another integrated circuit containing aHall sensor, depicted during formation of isolation layers. Theintegrated circuit 400 is formed in and on a substrate 402 having ap-type semiconductor material 404. The integrated circuit includes anarea for a Hall sensor 406, an NMOS transistor 408 and a PMOS transistor410. The integrated circuit 400 may include field oxide 414 disposed atthe top surface 412 of the substrate 402 to laterally isolate componentsand elements.

An isolation mask 456 is formed over the substrate 402 so as to exposean area for a first n-type isolation layer 420 in the area for the Hallsensor 406 and a second n-type isolation layer 436 under the area forthe NMOS transistor 408. The isolation mask 456 may be formed similarlyto the isolation mask 156 described in reference to FIG. 2A. In theinstant example, the area for the Hall sensor 406 and the area for theNMOS transistor 408 are separate. The isolation mask 456 covers the areafor the PMOS transistor 410. In the instant example, the isolation mask456 includes one or more blocking elements 474 in the area for the Hallsensor 406 for the purpose of diluting n-type dopants during asubsequent implant process. The blocking elements 474 may include aplurality of discrete blocking elements 474 a or one or more continuousblocking elements 474 b with apertures 476. The blocking elements 474may cover, for example, 20 percent to 80 percent of the area for theHall Sensor 406. In the instant example, the area for the NMOStransistor 408 is free of the blocking elements 474.

N-type dopants such as phosphorus are implanted into the substrate 402where exposed by the isolation mask 456; the n-type dopants are blockedfrom the substrate 402 by the isolation mask 456, including the blockingelements 474. The n-type dopants may be implanted at a dose and anenergy as described in reference to FIG. 2A, for example. The blockingelements 474 reduce the number of the n-type dopants per unit areareaching the substrate 402 in the area for the Hall sensor 406 comparedto the area for the NMOS transistor 408.

The isolation mask 456 is subsequently removed, for example by an ashprocess followed by a wet clean process. The implanted n-type dopantsare activated by an anneal process to form the first n-type isolationlayer 420 in the area for the Hall sensor 406 which provides a Hallplate 418 of the Hall sensor 406, and to form the second n-typeisolation layer 436 under the area for the NMOS transistor 408. Theanneal process may include a furnace anneal process or a rapid thermalanneal process. An average net dopant density of the Hall plate 418 islower than an average net dopant density of the second n-type isolationlayer 436, due to the n-type dopants blocked from the substrate 402 bythe blocking elements 474. The lower average net dopant density of theHall plate 418 may advantageously provide a higher sensitivity of theHall sensor 406 compared to a Hall sensor with a Hall plate having ahigher average net dopant density. Concurrently forming the secondn-type isolation layer 436 and the first n-type isolation layer 420 mayadvantageously reduce fabrication cost and complexity of the integratedcircuit 400 compared to forming the n-type isolation layers separately.In an alternate version of the instant example, the first n-typeisolation layer 420 and the second n-type isolation layer 436 may abouteach other, similar to the structure shown in FIG. 1.

FIG. 5A through FIG. 5C are cross sections of another integrated circuitcontaining a Hall sensor, depicted steps of formation of isolationlayers. Referring to FIG. 5A, the integrated circuit 500 is formed inand on a substrate 502 having a p-type semiconductor material 504. Theintegrated circuit includes an area for a Hall sensor 506, an NMOStransistor 508 and a PMOS transistor 510. The integrated circuit 500 mayinclude field oxide 514 disposed at the top surface 512 of the substrate502 to laterally isolate components and elements.

An isolation mask 556 is formed over the substrate 502 so as to exposean area for a first n-type isolation layer 520 in the area for the Hallsensor 506 and a second n-type isolation layer 536 under the area forthe NMOS transistor 508. The isolation mask 556 may be formed similarlyto the isolation mask 156 described in reference to FIG. 2A. In theinstant example, the area for the Hall sensor 506 and the area for theNMOS transistor 508 are separate. The isolation mask 556 covers the areafor the PMOS transistor 510. N-type dopants such as phosphorus areimplanted into the substrate 502 where exposed by the isolation mask556; the n-type dopants are blocked from the substrate 502 by theisolation mask 556. The n-type dopants may be implanted at a dose and anenergy, for example, as described in reference to FIG. 2A. The isolationmask 556 is subsequently removed, for example by an ash process followedby a wet clean process. The implanted n-type dopants are activated by ananneal process to form the first n-type isolation layer 520 in the areafor the Hall sensor 506 which provides a Hall plate 518 of the Hallsensor 506, and to form the second n-type isolation layer 536 under thearea for the NMOS transistor 508. The anneal process may include afurnace anneal process or a rapid thermal anneal process. In analternate version of the instant example, the anneal process may beperformed until a subsequent compensation implant is completed.Concurrently forming the second n-type isolation layer 536 and the firstn-type isolation layer 520 may advantageously reduce fabrication costand complexity of the integrated circuit 500 compared to forming then-type isolation layers separately.

Referring to FIG. 5B, a compensation mask 578 is formed over thesubstrate 502 so as to expose at least a drift region of the Hall plate518 as depicted in FIG. 5B, and possibly the entire Hall plate 518. Thecompensation mask 578 covers the areas for the NMOS transistor 508 andthe PMOS transistor 510. P-type dopants such as boron are implanted intothe substrate 502 in the area exposed by the compensation mask 578; thep-type dopants are blocked from the substrate 502 by the compensationmask 578. The p-type dopants are implanted at a dose and energy todistribute the p-type dopants throughout the Hall plate 518 at a dopantdensity lower than the n-type dopants in the Hall plate 518. The p-typedopants may be implanted at a dose, for example, of 50 percent to 80percent of the dose of the n-type dopants which were implanted to formthe first n-type isolation layer 520. The compensation mask 578 issubsequently removed, for example by a similar process used to removethe isolation mask 556 of FIG. 5A. The implanted p-type dopants areactivated by an anneal process to form a compensation well 580 whichcompensates the Hall plate 518. The implanted p-type dopants in thecompensation well 580 are distributed so as to reduce a net averagedoping density of the Hall plate 518 while maintaining an n-typeconductivity in the Hall plate 518. Reducing the net average dopingdensity of the Hall plate 518 advantageously improves a sensitivity ofthe Hall sensor 506. Reducing the net average doping density of the Hallplate 518 by the compensation well 580 may advantageously provide a moreuniform net doping density in a compensated portion of the Hall plate518. In an alternate version of the instant example, the compensationwell 580 may be formed prior to the first n-type isolation layer 520 andthe second n-type isolation layer 536.

Referring to FIG. 5C, formation of the integrated circuit 500 continueswith formation of a first shallow p-type well 524 and a second shallowp-type well 534 in the substrate 502. The first shallow p-type well 524is formed over, and extending to, the Hall plate 518. The second shallowp-type well 534 is formed in the second n-type isolation layer 536 inthe area for the NMOS transistor 508. The first shallow p-type well 524and the second shallow p-type well 534 are formed concurrently, forexample as described in reference to FIG. 2B, accruing the advantagesdisclosed therein. First shallow n-type wells 530 and a second shallown-type well 542 are formed concurrently in the substrate 502, in theareas for the Hall sensor 506 and the PMOS transistor 510, respectively.The first shallow n-type wells 530 provide electrical connections to theHall plate 518. The first shallow n-type wells 530 and the secondshallow n-type well 542 may be formed as described in reference to FIG.2C, for example, accruing the advantages disclosed therein.

An NMOS gate structure 538 of the NMOS transistor 508 and a PMOS gatestructure 544 of the PMOS transistor 510 are formed on the substrate502. N-type contact regions 532 and NSD regions 540 are formedconcurrently in the areas for the Hall sensor 506 and the NMOStransistor 508, respectively. The n-type contact regions 532 and the NSDregions 540 may be formed as described in reference to FIG. 2D, forexample, accruing the advantages disclosed therein. PSD regions 546 ofthe PMOS transistor 510 are formed as described in reference to FIG. 2E.In the instant example, a p-type region are not formed at a top surface512 of the substrate 502 in the Hall sensor 506 concurrently with thePSD regions 546, as described in reference to other examples herein.

In the instant example, a layer of silicide block dielectric 566 isformed over the first shallow p-type well 524. Subsequently, metalsilicide 528 is formed on exposed semiconductor material at the topsurface 512 of the substrate 502, including on the NSD regions 540 ofthe NMOS transistor 508, the PSD regions 546 of the PMOS transistor 510and the n-type contact regions 532 of the Hall sensor 506. The firstshallow p-type well 524 is free of the metal silicide 528 due to thelayer of silicide block dielectric 566.

A PMD layer 548 is formed over the field oxide 514, the metal silicide528, the layer of silicide block dielectric 566 and the gate structures538 and 544. The PMD layer 548 may have a similar structure to the PMDlayer 148 and be formed by the processes discussed in reference toFIG. 1. Contacts 550 are formed through the PMD layer 548 to makeelectrical connections to the Hall sensor 506, the NMOS transistor 508and the PMOS transistor 510 through the metal silicide 528. The contacts550 may be formed by etching contact holes through the PMD layer 548,and forming a titanium liner, by sputtering or an ionized metal plasma(IMP) process, on the PMD layer 548 and extending into the contactholes. A titanium nitride liner is formed, by reactive sputtering oratomic layer deposition (ALD), on the titanium liner. A layer oftungsten is formed, by a metal organic chemical vapor deposition (MOCVD)process, on the titanium nitride liner, filling the contact holes. Thetungsten, titanium nitride and titanium are removed from over a topsurface of the PMD layer 548 by a tungsten CMP process, leaving thetungsten fill metal, titanium nitride liner and titanium liner in thecontact holes to provide the contacts 550.

FIG. 6 is a cross section of another example integrated circuitcontaining a Hall sensor. The integrated circuit 600 has a substrate 602including a p-type semiconductor material 604. The integrated circuit600 includes a Hall sensor 606, a first NMOS transistor 608, a PMOStransistor 610 and a circuit component 682 disposed over a Hall plate618 of the Hall sensor 606. In the instant example, the circuitcomponent 682 is a second NMOS transistor 682. In the instant example,the Hall sensor 606 is a horizontal Hall sensor. A vertical Hall sensoris within the scope of the instant example. The integrated circuit 600may include field oxide 614 disposed at the top surface 612 of thesubstrate 602 to laterally isolate components and elements.

The Hall sensor 606 includes the Hall plate 618 disposed in a firstn-type isolation layer 620 in the substrate 602. An average net dopantdensity of the Hall plate 618 may be, for example, 5×10¹⁶ cm⁻³ to 1×10¹⁷cm⁻³. A thickness of the Hall plate 618 may be 0.5 microns to 1 micron.The average net dopant density and the thickness may provide a sheetresistance of 850 ohms per square to 2500 ohms per square of the Hallplate 618. The Hall sensor 606 includes a first shallow p-type well 624disposed in the substrate 602 over, and extending to, the Hall plate618. In the instant example, p-type regions 626 may be disposed in thefirst shallow p-type well 624, at the top surface 612 of the substrate602. The first shallow p-type well 624 may extend below the field oxide614. Electrical connections to the Hall plate 618 may be provided byfirst shallow n-type wells 630 disposed in the substrate 602; only onefirst shallow n-type well 630 is visible in FIG. 6. The first shallown-type wells 630 may be laterally separated from the first shallowp-type well 624 by elements of the field oxide 614. N-type contactregions 632 may be disposed in the substrate 602 over the first shallown-type wells 630 to reduce electrical resistance to the Hall plate 618.Metal silicide, a PMD layer and metal interconnects are not shown inFIG. 6, but are present in the completed integrated circuit 600.

The first NMOS transistor 608 is disposed over a second shallow p-typewell 634 disposed in the substrate 602. The first shallow p-type well624 of the Hall sensor 606 and the second shallow p-type well 634 havesubstantially equal distributions of p-type dopants such as boron as aresult of being formed concurrently, for example as described inreference to FIG. 2B. The second shallow p-type well 634 is contained ina second n-type isolation layer 636, which may be separate from thefirst n-type isolation layer 620 which provides the Hall plate 618 asdepicted in FIG. 6. Alternatively, the second shallow p-type well 634may be contained in a common n-type isolation layer which provides theHall plate 618, as described in reference to FIG. 1. In either case, thesecond n-type isolation layer 636 containing the second shallow p-typewell 634 and the first n-type isolation layer 620 which provides theHall plate 618 have substantially equal distributions of n-type dopantssuch as phosphorus as a result of being formed concurrently, for exampleas described in reference to FIG. 2A. The first NMOS transistor 608includes an NMOS gate structure 638 disposed over the second shallowp-type well 634 and NSD regions 640 disposed in the substrate 602adjacent to, and partially underlapping, the NMOS gate structure 638,similar to that described in reference to FIG. 1. The n-type contactregions 632 of the Hall sensor 606 and the NSD regions 640 havesubstantially equal distributions of n-type dopants such as phosphorusand arsenic as a result of being formed concurrently, for example asdescribed in reference to FIG. 2D.

The PMOS transistor 610 is disposed over a second shallow n-type well642 disposed in the substrate 602. The first shallow n-type wells 630 ofthe Hall sensor 606 and the second shallow n-type well 642 havesubstantially equal distributions of n-type dopants such as phosphorusas a result of being formed concurrently, for example as described inreference to FIG. 2C. The PMOS transistor 610 includes a PMOS gatestructure 644 and PSD regions 646 disposed in the substrate 602 adjacentto, and partially underlapping, the PMOS gate structure 644, similar tothat described in reference to FIG. 1. The p-type regions 626 of theHall sensor 606 and the PSD regions 646 have substantially equaldistributions of p-type dopants such as boron as a result of beingformed concurrently, for example as described in reference to FIG. 2E.

In the instant example, the second NMOS transistor 682 is disposed overthe first shallow p-type well 624 disposed over the Hall plate 618. Thesecond NMOS transistor 682 includes an NMOS gate structure 684 disposedover the first shallow p-type well 624 and NSD regions 686 disposed inthe substrate 602 adjacent to, and partially underlapping, the NMOS gatestructure 684, similar to that described in reference to FIG. 1. Thesecond NMOS transistor 682 may be part of a current source whichprovides current to the Hall sensor 606 or part of a voltage sensorwhich senses a voltage produced by the Hall sensor 606. Forming thesecond NMOS transistor 682 may advantageously reduce a size andfabrication cost of the integrated circuit 600. Other components may beformed in over the first shallow p-type well 624, accruing a similaradvantage.

An n-type well resistor 688 may be disposed in the substrate 602 underthe field oxide 614. The n-type well resistor 688 may be part of acircuit which includes the second NMOS transistor 682. The n-type wellresistor 688 may be advantageously formed concurrently with the firstshallow n-type wells 630 of the Hall sensor 606. Connections to then-type well resistor 688 may be provided by n-type contact regions 690,of which one instance is shown in FIG. 6, which may advantageouslyformed concurrently with the n-type contact regions 632 of the Hallsensor 606.

FIG. 7 is a cross section of another example integrated circuitcontaining a Hall sensor. The integrated circuit 700 has a substrate 702including a p-type semiconductor material 704. The integrated circuit700 includes a Hall sensor 706, a first NMOS transistor 708, a PMOStransistor 710 and a circuit component 792 disposed over an n-type Hallplate 718 of the Hall sensor 706. In the instant example, the circuitcomponent 792 is a p-type Hall plate 792. In the instant example, theHall sensor 706 is a horizontal Hall sensor. A vertical Hall sensor iswithin the scope of the instant example. The integrated circuit 700 mayinclude field oxide 714 disposed at the top surface 712 of the substrate702 to laterally isolate components and elements.

The Hall sensor 706 includes the n-type Hall plate 718 disposed in afirst n-type isolation layer 720 in the substrate 702, as described inthe examples herein. Electrical connections to the n-type Hall plate 718may be provided by first shallow n-type wells 730 disposed in thesubstrate 702. N-type contact regions 732 may be disposed in thesubstrate 702 over the first shallow n-type wells 730 to reduceelectrical resistance to the n-type Hall plate 718.

The Hall sensor 706 includes a first shallow p-type well 724 disposed inthe substrate 702 over, and extending to, the n-type Hall plate 718. Thefirst shallow n-type wells 730 may be laterally separated from the firstshallow p-type well 724 by elements of the field oxide 714. In theinstant example, field oxide 714 is disposed in the first shallow p-typewell 724, at the top surface 712 of the substrate 702. The first shallowp-type well 724 extends below the field oxide 714. The first shallowp-type well 724 provides the p-type Hall plate 792 over the n-type Hallplate 718. Electrical connections to the p-type Hall plate 792 areprovided through openings in the field oxide 714 within the firstshallow p-type well 724. P-type contact regions 794 may be formed in theopenings to reduce electrical resistance of the connections to thep-type Hall plate 792. The p-type Hall plate 792 may be part of the Hallsensor 706 to improve a sensitivity of the Hall sensor 706, or may bepart of a second Hall sensor in the integrated circuit 700. Forming thep-type Hall plate 792 over the n-type Hall plate 718 may advantageouslyreduce size and fabrication cost of the integrated circuit 700.

The first NMOS transistor 708 is disposed over a second shallow p-typewell 734 contained in a second n-type isolation layer 736, disposed inthe substrate 702. The second shallow p-type well 734 and the secondn-type isolation layer 736 are formed concurrently with the firstshallow p-type well 724 and the first n-type isolation layer 720,respectively. The first NMOS transistor 708 includes an NMOS gatestructure 738 and NSD regions 740 similar to those described inreference to FIG. 1. The PMOS transistor 710 is disposed over a secondshallow n-type well 742 disposed in the substrate 702. The first shallown-type wells 730 of the Hall sensor 706 and the second shallow n-typewell 742 are formed concurrently. The PMOS transistor 710 includes aPMOS gate structure 744 and PSD regions 746 similar to those describedin reference to FIG. 1.

Metal silicide 728 may be formed on exposed semiconductor material atthe top surface 712 of the substrate 702, to reduce electricalresistance of connections to the n-type contact regions 732 for then-type Hall plate 718, to the p-type contact regions 794 for the p-typeHall plate 792, to the NSD regions 740 and to the PSD regions 746. A PMDlayer 748 and contacts 750, for example as described in reference toFIG. 1, are disposed over the top surface 712 of the substrate 702.Layers of metal interconnects and dielectric material, not shown in FIG.7, are disposed above the PMD layer 748 to provide electricalconnections between the components of the integrated circuit 700. Theintegrated circuit 700 accrues the advantages discussed in reference tothe integrated circuit 100 of FIG. 1.

FIG. 8 is a cross section of another example integrated circuitcontaining a Hall sensor. The integrated circuit 800 has a substrate 802including a p-type semiconductor material 804. The integrated circuit800 includes a Hall sensor 806, and an NMOS transistor and a PMOStransistor, not shown in FIG. 8. In the instant example, the Hall sensor806 is a vertical Hall sensor. A horizontal Hall sensor is within thescope of the instant example. The integrated circuit 800 may includefield oxide 814 disposed at the top surface 812 of the substrate 802 tolaterally isolate components and elements.

The Hall sensor 806 includes a Hall plate 818 with a non-linearconfiguration, in the instant example, a closed-loop configuration,disposed in an n-type isolation layer 820 in the substrate 802. Otherconfigurations of the Hall plate 818 are within the scope of the instantexample. Electrical connections to the Hall plate 818 may be provided byshallow n-type wells 830 disposed in the substrate 802, around theclosed loop. A plurality of shallow p-type wells 824 are disposed in thesubstrate 802 over the Hall plate 818 around the closed loop between theshallow n-type wells 830. The shallow n-type wells 830 may be laterallyseparated from the shallow p-type wells 824 by elements of the fieldoxide 814. N-type contact regions 832 may be disposed in the substrate802 over the shallow n-type wells 830 to reduce electrical resistance tothe Hall plate 818. In the instant example, n-type regions 896 areformed in the substrate 802 over the shallow n-type wells 830, extendingto the top surface 812. The advantages discussed in reference to otherexamples disclosed herein may be accrued by the integrated circuit 800.Forming the isolation layer 820 to provide the Hall plate 818advantageously enables a Hall sensor 806 with a desired configuration.Metal silicide, a PMD layer and metal interconnects are not shown inFIG. 8, but are present in the completed integrated circuit 800.

While various embodiments of the present disclosure have been describedabove, it should be understood that they have been presented by way ofexample only and not limitation. Numerous changes to the disclosedembodiments can be made in accordance with the disclosure herein withoutdeparting from the spirit or scope of the disclosure. Thus, the breadthand scope of the present disclosure should not be limited by any of theabove described embodiments. Rather, the scope of the disclosure shouldbe defined in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A Hall sensor, comprising: A substrate having asurface; first and second silicide layers spaced apart from each otheralong the surface; a first doped region extending from the firstsilicide layer, and having a first dopant density; a second doped regionextending from the second silicide layer and laterally isolated from thefirst doped region, the second doped region having the first dopantdensity; and a doped layer positioned under and connecting between thefirst doped region and the second doped region, the doped layer having asecond dopant density lower than the first dopant density.
 2. The Hallsensor of claim 1, further comprising: a current source coupled betweenthe first silicide layer and the second silicide layer.
 3. The Hallsensor of claim 1, further comprising: a third doped region positionedabove the doped layer and laterally between the first doped region andthe second doped region, the third doped region having a firstconductivity type, wherein each of the first doped region, the seconddoped region, and the doped layer has a second conductivity typeopposite of the first conductivity type.
 4. The Hall sensor of claim 1,further comprising: an isolation structure positioned above the dopedlayer and laterally between the first doped region and the second dopedregion, wherein each of the first doped region, the second doped region,and the doped layer has a single conductivity type.
 5. The Hall sensorof claim 1, further comprising: a third silicide layer spaced apart andbetween the first silicide layer and the second silicide layer along thesurface; and a third doped region extending from the third silicidelayer and laterally isolated from the first doped region and the seconddoped region, the third doped region having the first dopant density,wherein each of the first doped region, the second doped region, thirddoped region, and the doped layer has a single conductivity type.
 6. TheHall sensor of claim 5, further comprising: a voltage sensor coupled tothe third silicide layer.
 7. The Hall sensor of claim 5, furthercomprising: a fourth doped region positioned above the doped layer andlaterally between the first doped region and the third doped region, thefourth doped region having a first conductivity type, wherein the singleconductivity type of the first doped region, the second doped region,third doped region, and the doped layer is a second conductivity typeopposite of the first conductivity type.
 8. The Hall sensor of claim 5,further comprising: a fourth doped region positioned above the dopedlayer and laterally between the second doped region and the third dopedregion, the fourth doped region having a first conductivity type,wherein the single conductivity type of the first doped region, thesecond doped region, third doped region, and the doped layer is a secondconductivity type opposite of the first conductivity type.
 9. The Hallsensor of claim 1, wherein the doped layer includes a center portionfree of overlapping the first doped region and the second doped region,the center portion has a third dopant density lower than the seconddopant density.
 10. The Hall sensor of claim 1, further comprising: athird doped region laterally surrounding the first doped region and thesecond doped region, the third doped region having the second dopantdensity and a greater depth from the surface than the first doped regionand the second doped region, wherein the doped layer is a bottom portionof the third doped region.